fix: close(immediate) and dequeue_event exceptions for EventConsumer compatibility

[TadakiAsechi]

Summary

Adds close(immediate: bool) to RedisStreamsEventQueue ( Fixes #11 )
and aligns dequeue_event() with EventConsumer (TimeoutError / QueueEmpty). ( Fixes #12 )

Changes

• Close:
  • close(immediate=True) runs pending cleanup (xpending_range + xack);
  • immediate=False sets _closing only.
  • New _close_pending_cleanup();
  • manager.close() calls queue.close(immediate=True).
• Dequeue:
  • dequeue_event() raises asyncio.TimeoutError or asyncio.QueueEmpty (no RuntimeError wrap).

Testing

pytest tests/